We have demonstrated that aqueous extract of a pantropical plant, Phyllanthus nitruri, inhibits in vitro reverse transcriptase (RT) from several retroviruses: namely, Rous Sarcoma Virus (RSV), Moloney Murine Leukemia Virus (MoMLV) and most importantly, Human Immunodeficiency Virus (HIV), The specific aims of this project are co isolate and purify individual components of the extract which show antiviral activity and to study their chemical structure and antiviral activity against HIV. Preliminary studies on fractionation of the extract by chromatography on Sephadex G1O column indicated that two fractions, one with molecular weight (Mw) > 1000 and another with Mw approximately 350, inhibit HIV RT and also protect T lymphoid cell line C3 from infection with HIV. First, the extract will be fractionated on a scaled-up version of Sephadex G1O column. The fractions which show antiviral activity against HIV will be further purified by High Performance Liquid Chromatography (HPLC) on C-18 reverse phase column and the individual components will be examined for inhibition of HIV RT and also for protection of T lymphocytes against infection by HIV. The active components will then be studied further to elucidate their chemical structure using chemical and physicochemical analyses including Ultraviolet, Infrared, Nuclear Magnetic Resonance and Mass Spectrometry. It is anticipated from preliminary studies that these components may represent a new class of non-nucleoside antiviral agents with very low toxicity, suitable for chronic therapy for HIV infection.